Production of aromatic derivatives



Patented July 16, 1946 l PRODUCTION OF AROMATIC DERIVATIVES William N. Axe, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application July 3, 1944, Serial No. 543,421

12 Claims. (01. zed-e71) This invention relates to derivatives of aromatic compounds. In one modification it relates to alkenyl derivatives of aromatic compounds. In another modification it relates to normal alkyl derivatives of aromatic compounds. As specific modifications it relates to the alkenylation of aromatic hydrocarbons and to the production of normal alkyl derivatives of aromatic hydrocarbons. This application is a continuation-inpart of my copending application Serial No. 433,- 192, filed March 3, 1942.

Normal alkenyl aromatic compounds and normal alkyl aromatic compounds are valuable intermediate compounds both in their own rights and as intermediates in organic syntheses. They may be used for the production of normal aliphatic derivatives of such compounds as aminobenzenes, aminonaphthalenes, phenols, naphthols, aminophenols, aminonaphthols, quinolines, and the like. These materials can be used in the preparation of oxidation inhibitors, pharmaceuticals, dyestuffs, and explosives. The development of the full potentialities of normal aliphatic derivatives of such compounds has been precluded by the absence of suitable sources of such compounds. Thus, when olefins are used to alkylate aromatic compounds the normal alkyl derivative is produced only in the case of ethylene and with other olefins it is impossible to produce a normal alkyl derivative by catalytic alkylation. Synthetic methods for the production of normal alkyl derivatives have been limited heretofore to reactions of the Wurtz-Fittig type in which aromatic halides have been condensed, in the .presence of a metal such as sodium, with normal a1- kyl halides. The best yields reported for such reactions have not exceeded about 30per cent of the theoretical yield and more often actual yields are from about to percent of the theoretical yields. Other disadvantages of such synthesis operations include the use of large quantities of metals such as sodium with appreciable attendant hazards, the employment of expensive intermediate compounds, the necessity of special solvents, and the relatively diflicult production of normal alkyl halides- An object of this invention is to produce normal aliphatic derivatives of aromatic compounds.

Another object of this invention is to produce normal alkyl derivatives of aromatic compounds.

A further object of this invention is to produce normal alkenyl derivatives of aromatic compounds.

A still further object of this invention is to react low-boiling aromatic hydrocarbons-with 10w:

' boiling normal l,3- diolefin s to produce normal tion will become apparent to one skilledin the art from the accompanying disclosure and discussion.

I have now found that aromatic compounds, including aromatic hydrocarbons, phenols, naphthols, and aromatic halides, can be reacted with normal 1,3-diolefins to produce alkenyl derivatives of said aromatic compounds. I have. further found that such alkenyl derivatives include normal monoalkenyl derivatives whichcan be successfully subjected. to nondestructive hydro e genation to produce thecorrespondingnormalalkyl derivatives. 1 have .further discovered. that such derivatives can beproduced in extremely highyields ,and can be recovered in substantial quantities in a condition of high purity. As the aromatic reactant of my process I prefer to use benzene, naphthalene, simple alkyl derivatives of these hydrocarbons such as toluene, ethylbenzene, xylenes, and'the like, phenol, naphthols,

and simple alkyl derivatives of these materials, and aromatic halides such as phenyl chloride, phenyl bromide, one of the naphthyl chlorides. and the like, although other alkenylatable aromatic compounds are notto be excluded from the broad concept of my invention. As the diolefin reactant I prefer to use a low-boiling normal, 1,3- diolefin such as 1,3-butadiene, l, 3-pentadiene, 1,3-hexadiene, and the like. Although it is a primary object of my invention to produce normal aliphatic derivatives by the use of normal l,3-di olefins, it is to be understood that alkyl derivatives of normal 1,3-diolefins, such as S-methyll,3-hexadiene and 6-methyl-l,3-heptadiene, to produce aromatic derivatives such as l-phenyl- G-methyl heptylene, andthe like, are not to be excluded from the broad concepts of my invention.

- Broad'features of this process may be more readily understood by considering a typical procedure.

which the benzene is present in substantial mo- A blend of butadiene in benzene, in

boron fluoride and the excess benzene is recoV-.

ered by fractional distillation. The debenzenized product is further fractionally distilled to separate a main product (normal butenyl benzene, or.

phenyl butene) boiling at about 365to about 370 F., and a higher-boiling kettle product. main product fraction may be hydrogenated over a conventional hydrogenation catalyst such as Raney nickel, platinum or any of the .morerugged industrial hydrogenation catalysts to yield n-butylbenzene, which ordinarily requires no further purification.

I have found that efficient catalysts for such alkenylation reactions can be prepared by substantially saturating water with a boron trihalide.

A preferred boron trihalide is boron trifluoride,

although I do not intend to exclude other boron trihalides, particularly boron trichloride and boron tribromide which are low-boilingmaterials. A preferred catalyst for use in myprocess is conveniently prepared bypassing gaseous boron fiuoride into water until the desired hydrate concentration is realized. The resulting hydrate is aliquid of relatively high specific gravity and substantially immiscible with hydrocarbons. During this reaction considerable heat is evolved and suitable means for cooling should be provided. Since the specific gravity of a completely saturated solutionis approximately 1.77, convenient control of concentration can'be effected by means of hydrometer determinations. Means for mechanicalagitation of the absorbent liquid may be used, andIhaJyefouhd that such means are often The helpful in obtaining some of the higher concentrations of the hydrate used in the process. In the preparation of the catalyst, the gaseous boron fiuoridemay be passed into waterwhilethe temperaturei's maintained below 150 F. and preferablyabove-75" F., untilthe water is saturated and boron fluoride passes through'unabsorbed. At this point a water-boronifluoride mol ratio of approximately 1:1 is ordinarily obtained. The catalyst may be, used in this form, or water may be added until a desired higher mo'l ratio is .obtained; alternately, the addition of boron fluoride may be halted at the desired hydrate concentra tion by determination of the increase in weight or specific gravity of the liquid. Preferably, the alkenylation catalyst of this invention comprises a hydrated boron fluoride containing from about 1.0 to about 1.5 mole of water per mol of- :boron fluoride; This catalyst preparation reaction may be conducted, if desired, under pressure, particularly when using boron trifluoride or boron trichloride. When an active catalyst of this invention loses appreciable quantities of boron trifluoride or other boron trihalide during use, its activity decreases andfor this reason it is desirable to add during a continuous process small amountsof boron trihalide initially used to prefpare the catalyst, continuously or intermittently,

5 activated bauxite, and the like, although when using 'boron trifiuoride-containing complexes it is derivatives.

4 preferable not to use a granular material contain ing appreciable amounts of silica.

In the alkenylation step the reaction appears to be primarily mono-alkenylation to form monoalkenyl derivatives of the aromatic compound. It also appears that secondary reactions take place to certain extents, including cyclization and/or polymerization of the resulting monoalkenyl This conclusion is based on the observation that the aromatic compound reacted is molecularly equivalent to the diolefin reacted. If extensive polyalkenylation occurred, to form di- ;or tri-alkenyl aromatic derivatives, the amount of aromatic hydrocarbon reacted would be substantially less than the molecular equivalent'of the diolefin, while if the monoalkenyl derivative entered into reaction with the aromatic hydrocarbon, to form th corresponding di-substituted parafiin hydrocarbon, the amount of aromatic hydrocarbon reacted would be substantially greater than .a molecular equivalentof the diolefin. No appreciable polymerization ofthe diolefin is believed to take place under preferred conditions of operation, a conclusion deducedfrom a consideration of. the relativeamounts of reactants which undergo reaction and from the characteristics of such high-boiling products. Such results contrast with the results obtained when catalysts such as sulfuric acid are used with the same reactants. Thus, when benzene and 1,3-butadiene are reacted in the presence of sulfuric acid it has been reported that the product is diphenylbutane and that no phenylbutene is produced.

and conveniently conducted ata temperature -be-' tween about '70 and about 150 F., with a temperature between about'SO to F. and about 1.10

to F. being preferred; Temperatures above F., or below 70 F;, arejnot tob'e. excluded, however. The. average'reaction time may be between a few minutes and a few hours, with satis-. factory results being obtained with a reaction time between about 5 and about 20 minutes. The molar ratio of aromatic compounds to diolefin in the feed to a continuous reaction :step may be between about 2:1 and about lozlwith satisfactory operation generally being obtained with aratio between about 4 :1 and about 6: 1. Intimate mixing of the reaction mixture, accompanied. by recirculation, will generally result in higher effective ratios. in the reaction .zone.- In some instances it isdesirable to use moderate superatmospheric pressures, particularly with the lower boiling reactants, but generally the pressure need not be appreciably above that which will insure that the reactants are present in liquid phase and to insure that the catalyst is adequately saturated with the boron trihalide. As previously stated it is preferred that the reacting mixture and the catalyst be intimatelyadmixed. This may be accomplished by efficient stirring mechanism, by continuously recirculating in a closed cycle a substantial amount of the reaction mixture comprising. reactants, products and catalyst, by pumping such. a reaction mixture through a long tube coil at. a rate such that conditions of turbulent flow exist, or by other means well known to those skllledin the art of hydrocarbon alkylations. It is preferred that the reaction mixture contain at least about 5 per cent by volume off-the catalyst and that. the

amount of catalyst present should not exceed that which will permit a continuous phase of reacting materials when the reaction mixture is intimately admixed. Thus it is desired that the. catalyst phase not be the continuous phase when a liquid catalyst is used. Inert materials may be present during the reaction, such as relatively nonreactive impurities normally accompanying the reactants, added low-boiling, paraflin hydrocarbons such as a paraifinic naphtha fraction,orthe like.

When 1,3-butadiene is the diolefi'nreactant the monoalkenyl product is substantially completely the normal alkenyl derivative. 'With diolefin reactants containing a liigher number 'of carbon atoms per molecule-suchhighi'yields" of the normal derivative will often notbe obtained but it will still be possible to obtain quite sub stantial yields of the normal alkenyl derivative. In any case a fraction containing, or "comprising essentially, the desired normal alkenyl derivative may be readily separated from the reaction eiliuents, generally by passing the effluents to a settling chamber wherein the catalyst separates from a liquid phase containing unreacted charge stock and reaction products, and separating from this liquid phase, as by fractional distillation, a fraction of any desired purity.

As will be appreciated the normal alkenyl derivative may, in many instances, be a desired product of the process. However, I have found that this material may be readily converted to the normal alkyl derivative by nondestructive hydrogenation. This hydrogenation will most often be conducted. in a manner such that the alkenyl group is saturated by hydrogen. However, it will be appreciated that, particularly when aromatic hydrocarbons are reacted in accordance with my invention, not only may normal alkyl derivatives thereof be produced by such a nondestructive hydrogenation, but the hydrogenation may be extended to include partial or complete saturation of the aromatic nucleus. Thus it is possible to react a benzene with a lowboiling 1,3-diolefin to produce a normal alkenyl derivative of said benzene, and subsequently to hydrogenate this product, in one or more steps, to produce a normal alkyl derivative or a corresponding normal alkyl cyclohexane. Likewise, a naphthalene may be converted to a normal alkenyl derivative, and this product may subsequently be hydrogenated, in one or more steps,

to produce a normal alkyl derivative, a normal alkyl tetralin, or a normal alkyl decalin. For such hydrogenations any suitable known nondestructive hydrogenation catalyst may be employed which is capable of effecting saturation of the alkenyl group without saturation of the aromatic nucleus or without reaction of any other reactive group in the alkenyl compound.

So-called Raney nickel has been found desir-- able in accomplishing this result when the hydrogenation is conducted at moderate temperatures and pressures. More drastic hydrogenation conditions will be necessary in order to produce the more saturated products just discussed. Thus, in the selective hydrogenation of the olefinic linkage, the rate of absorption of hydrogen may amount to about 1 mol per hour at pressures of 20 to 50 pounds per square inch and temperatures ranging from about '75 to about 150 F. Nuclear hydrogenation can be effected.

with the same catalyst at pressures of about 500 to 5000 pounds per square inch and at tem-' peratures of about 250 to 350 F. V

The following examples illustrate my invention further. However, it is to be understood that specific limitations expressed in such examples-are not to be. used to restrict my inven- 1.5 mols of water to one mol of boron fluoride wassuspended in 312 grams of benzene by agitation. Butadiene was introduced at a flow rate of 15 grams per houruntill50 grams had been absorbed. The reaction was carried out at 89 to 95 F. The alkylate was processed as above and the benzene-free alkylate was fractionated to yield 300 grams yield) of phenyl-butenes boiling between 356 to 365 F. (uncorr.).

Example II Operating under conditions similar to those given in Example I, toluene may be reacted with piperylene (1,3-pentadiene) to produce npentenyltoluene. In this instance, the toluenefree product is subjected to a preliminary fractionation under 10 mm. pressure to effect a rough separation of higher-boiling products from the pentenyltoluene. Final purification involves fractional distillation at atmospheric pressure to give a product boiling at about 430-440 F. amouning to about 60 per cent of the total alkenylate. Analytical data and oxidation reactions indicate this materialto be essentially 1 (p-tolyl)-2-pentene. Nondestructive hydrogenation results in quantitative reductions to 1emethyl-4rn-pentylbenzene having substantially the same boiling range as the original alkenyl derivative.

Although I have described my invention in considerable detail, with the inclusion of certain specific embodiments, it is not intended that the scope of the invention be limited unduly by such details. I claim:

1. A process for the production of normal aliphatic derivatives of aromatic compounds, which comprises reacting an aromatic compound with a normal 1,3-diolefin in the presence of a complex catalyst resulting from substantially saturating water with a boron trihalide.

2. A process for the production of normal alkyl derivatives of aromatic compounds, which comprises reacting an aromatic compound with -a normal 1,3-diolefin in the presence of a complex catalyst resulting from substantially saturating Water with a boron trihalide to form .a

normal alkenyl derivative of said aromatic com- I pound, separating from efiluents of said alkenylation a fraction comprising said normal alkenyl derivative, and subjecting said fractionto nondestructive hydrogenation to form a normal alkyl derivative of said aromatic compound.

3.-A process for the alkenylation of an aromatic hydrocarbon, which comprises reacting a low-boiling normal 1,3-diolefin hydrocarbon with a molar excess of an alkenylatable aromatic-hydrocarbon under alkenylation conditions in the presence of a catalyst resulting from saturating water with boron trifluoride.

4. The process of claim 3 wherein said diolefin is 1,3-pentadiene.

5. The process of claim 3 Whereinsaid are-'- matic hydrocarbon is naphthalene" and said diolefin is 1,3-butadiene.

6. A process for the production of a normal.

alkyl benzene, which comprises reacting a mixture comprising a low-boiling normal 1,3-dio1efin and a molar excess of benzene under alkenyla- 'tion conditions in the presenceof a catalyst'reisulting from saturating water" with boron trie fluoride to produce a normal monoalkenyl deriva- 'tive of benzene, separating from efliuents of said alkenylation a fraction comprising said normal monoalkenyl derivative, and subjecting said fraction to nondestructive hydrogenation under co'nditionssuch that substantially only said alkenyl group is saturated with hydrogen. I I v 7. The process of claim fiwherein said. diolefin is 1,3-butadiene and normal butylbenzene is, pro.- duced. v V g 8. Theprocess of claim 6 wherein said diolefin is 1,3-pentadiene and normal'pentylbenzene is,

produced. 7

9.'A process for the production of an aryl butene, which comprises reacting an alkenylatable; aromatic hydrocarbon'with 1,3-butadiene at a reaction temperature not greater than about 120 F., and with a substantial molar excess of said aromatic hydrocarbon, in the presence, as a catalyst, of a complex resulting from reacting boron fluoride with about 1 to about 1.5 molar equivalents of-water. j

10. A process for the alkenylation of an arc matic hydrocarbon, which comprises reacting'a low-boiling-normal 1,3-diolefin hydrocarbon with a molar excess of an alkenylatable aromatic hy drocarbon at a temperature of about '70 to about 150? F. and under sufficientpressure to maintain the reactants in the liquid phase in the presence of acatalyst resulting from saturating Water with boron trifluoride.

'11.'A process for the production of normal square inch and a temperature between about and maintaining a reaction time between about 5 and to about 20 minutes.

12. A process for the production of a normal alkyl'aromatic. hydrocarbon, which comprises reacting arr-aromatic hydrocarbon with a normal 1,3-diolefin at areaction temperature between about 70 and about F. and under a pressure sufficient to maintain thereactants in the liquid phase, said aromatic hydrocarbon and said diolefin being in a ratio'of about 2:1 to 10:1 of aromatic hydrocarbon to diolefin', in the presence of a catalyst comprising a liquid'complex resulting from saturating water with boron trifluoride;

maintaining a reaction time between about 5 and rabout 20'minutes whereby to form an alkenyl aromatic hydrocarbon; and non-destructively hydrogenating said alkenyl aromatic hydrocarbon to a normal alkylaromatic hydrocarbon in the presence of a nickel hydrogenation catalyst at a pressure of about 20 to about 50 pounds per and about 150-F.

' WILLIAM N. AXE. 

